The Oil Disaster Deepens

British Petroleum (BP) clean-up crews began the latest effort today to contain the massive crude oil leak in the Gulf of Mexico, off the coast of Louisiana. Workers are using remote-controlled submarines and a giant saw to cut into one of the undersea oil well's damaged pipes. Engineers will then try to place a cap on top to control the spill and siphon the oil into a tanker.

BP's plan hit a snag, though, when the saw got stuck in the pipe, said U.S. Coast Guard Admiral Thad Allen at a news conference. The goal is to free the blade, put in a new blade and finish the cut later in the day, Allen said. If the cap works, it should collect the "vast majority" of the oil, BP's chief operating officer Doug Suttles told CNN's John King.

But success depends on how smoothly workers can cut through the pipe. The more precise the cut, the better the cap will fit. However, the procedure could temporarily increase the flow of oil by as much as 20 percent. That's at least 100,000 gallons more a day. Workers have begun drilling a pair of relief wells to plug the leak, but that won't be complete until August.

Black Tide Rising

Thick, rust-colored oil has been gushing into the Gulf since April 20, when the Deepwater Horizon oil rig exploded, killing 11 workers on board. Since the blast, an estimated 210,000 gallons of oil have been spewing daily from an undersea well, located 5,000 feet below the disaster site.

In the six weeks since the explosion, an estimated 20 million to 40 million gallons of oil has been released into the ocean. It is the biggest oil spill in U.S. history. The last major slick occurred in 1989 when the Exxon Valdez hit a reef off the coast of Alaska, spilling 11 million gallons of oil.

BP has made several failed attempts to stop the leak. Remote-controlled submarines have been unable to shut off the well. BP also tried to contain the oil leak by lowering a 100-ton box over the well, but the attempt failed when ice-like crystals formed on the box. Plans to cover the leak by pumping mud and concrete into the well were also unsuccessful.

Marine Life at Risk

The sticky substance has already polluted 125 miles of Louisiana coastline, and oozed onto the coasts of Mississippi and Alabama. The oil could reach the white-sand beaches of Florida for the first time today. More and more oil-soaked sea animals are being found on the shores every day. Fishing, which is a major industry in the region, has also been halted.

Scientists say the inky slick is spreading underwater too. Tony Hayward, the head of BP, says this is not true. But researchers have found evidence of huge plumes of oil thousands of feet below the surface. A plume is a vertical body of fluid that rises or expands. "It's out of sight and out of mind," says Doug Rader, the chief ocean scientist for the Environmental Defense Fund. "But it will have a huge effect on the marine life in that zone."